Recently, bacteriological researches on periodontal diseases have advanced and, as the results, it has been found that many spirochetes are detected in sites with periodontal diseases and have good correlation with various clinical indices. Further, it has been also found that anaerobic gram negative bacteria are main pathogenic oral microorganisms for periodontal diseases. Among them, Black-pigmented Bacteroides such as B. gingivalis are particularly noted and many reports about their phathogenicities are present.
Then, attempts are made to detect these pathogenic bacteria in the oral cavity and to apply the results to clinical use so that periodontal diseases can be prevented or treated by diagnosing contraction or progress thereof.
However, there are some drawbacks in detection of these pathogenic oral bacteria by a bacteriological method. For example, detection requires highly skilled technique and special equipments such as use of a dark field microscope and handling of anaerobes, and involves complicated operations. Further, it takes long time and requires skill for cultivation and analysis of the result. Therefore, there are still many difficulties in application thereof to clinical practice.
From the immunological point of view, some attempts are made to detect the presence of the pathogenic microorganisms by determining antibody titer in blood which is humoral immunity to the pathogenic microorganisms, or determining lymphocyte blastformation which is cellular immunity. However, preparation of a specimen requires complicated operations and practical application is still difficult.
Under these circumstances, the present inventors have studied intensively to make detection of the pathogenic oral microorganisms for periodontal diseases applicable to clinical practice possible. As the result, the present inventors have found that some spirochetes in the oral cavity have periodontopathic bacteria specific aminopeptidase activities and Black-pigmented Bacteroides such as B. gingivalis, B. intermedius, B. corporis, B. melaninoqenicus, B. denticola and the like also have similar activities, which can be detected specifically, readily and promptly using particular substrates with precisely reflecting periodontal disease conditions.
It has been known heretofore in the prior art that oral spirochetes and B. gingivalis produce a trypsin-like enzyme and fibrinolysin [see, Journal of Clinical Microbiology, 97-102 (January, 1982); Microbios Letters, 25, 157-160 (1984); Journal of Dental Research, 65, 11, 1335-1340 (November, 1986) and Journal of Periodontal Research, 21, 95-100 (1986)]. However, it is difficult to use these enzymes as indices because of problems in correlation with clinical conditions and specificity in detection.